Hydraulic system



Nov. 2, 1943. w, R T 2,333,530

HYDRAULIC SYSTEM Filed Ap ril 25. 1942 2 Sheets-Sheet 1 mvzn'ron WALTERERNST BY- j ATTORNEY Nov. 2; 1943. w. ERNST HYDRAULIC SYSTEM Filed April25, 1942 2 Sheets-Sheet 2 ATTORNEY for instance, a variable deliverypump,

Patented Nov. 2, 1943 HYDRAULIC SYSTEM Walter Ernst, Mount G TheHydraulic Develo .ilcad, Ohio, assignor to pment Corporation, Inc.,

- Wilmington, Del., a corporation of Delaware Application April 25,1942, Serial No. 440,526

(Cl. Bil -97) 6 Claims.

This invention relates to hydraulic machinery and, in particular, tohydraulic'systems including a plurality of fluid operable motors and apressure fluid source of variable delivery, which is common to saidmotors, for'supplying pressure fluid thereto, and has associatedtherewith a control device adapted, in response .to a predeterminedpressure acting on said control device, to

reduce the delivery of the fluid source.

Heretofore, when trying to operate two or more hydraulic motors in ahydraulic system of the above mentioned type, it was always necessary toset the control device for the maximum pressure required in any of thehydraulic motors. In other words, even when the fluid pressure source,was idling, it continuously had to maintain the highest pressurerequired in the hydraulic system, which caused rapid wear of the pump.

Accordingly, it is an object of this invention to provide a hydraulicsystem with a plurality of hydraulic motors and a pressure fluid sourcecommon thereto, which will overcome the drawback outlined above.

It is another object of the invention to provide a hydraulic systemincluding a plurality of hydraulic motors and a pressure fluid source ofvariable delivery with a control device for varying the delivery, inwhich the control device may .be set so that the pressure fluid source,when idling, operates only at the lower rather than the higher pressurerequired in the hydraulic system.

Still another object of the invention consists in the provision of ahydraulic system including a plurality of hydraulic motors and avariable delivery pump with servomotor means, in which the servomotormeans may be'set so that the pump may selectively be shifted to and heldin substantially neutral or no delivery po'sitionin response to thelowest pressure required in the system.

It is a still further object of the invention to provide a hydraulicsystem with at least three hydraulic motors adapted respectively to beoperated at difierent pressures by a common variable delivery pump withservomotor means, in which the pump may be held in idling position atthe lowest pressure required in the hydraulic system.

These and other objects and advantages of the invention will appear moreclearly in connection with the accompanying drawings, in which:

Figure 1 diagrammatically illustrates a first embodiment of theinvention. I

Figures 2, 3 and 4 show various positions of a valve used in connectionwith the hydraulic system of Figure 1.

Figure 5 is a further embodiment of the invention.

General arrangement According to the present invention, the variabledelivery pump, adapted to supply pressure fluid to a plurality ofhydraulic motors at different pressures, is provided with differentialcontrol plunger means, the largest area of which is continuouslyconnected with the pressure side of the pump, while a smaller opposingarea may selectively be connected with the pressure side of the pumpwhen the latter supplies pressure fluid to a motor in the system whichrequires the maxi-' I mum pressure obtainable in the hydraulic system.Structural arrangement Referring now to the drawings and Figure 1thereof in particular, the hydraulic system shown therein comprises ahigh pressure motor, generally designated l and two low pressure motors,generally designated 2, 3. The motor I includes a cylinder 4 havingreciprocably mounted therein a piston 5 with piston rod 6. The motors I,2 and 3 are adapted to be supplied with pressure fluid from a variabledelivery pump 1, of any standard design, having a flow-control member 8,the position of which controls the delivery .of the pump.

The pump 1 includes a casing 9 housing a spring In, one end of whichabuts a spring disc H adjustable by means of an adjusting screw l2. Theother end of the spring I0 engages a head l3 of a control rod I4 which,in its turn, engages the flow-control member 8. The spring I0continuously urges the flow-control member 8 into position for placingthe pump 1 on full delivery stroke. The pump 1 has associated therewitha control mechanism, generally designated I5, which includes a casing l6connected to the pump casing in any convenient manner. The casing l6comprises a, cylinder bore I 1 and a chamber l8.

The cylinder bore H has reciprocably mounted therein a differentialpiston IS with an extension 20 adapted to engage the flow-control member8 and, in response to a. predetermined pressure in the bore IT, to shiftthe flow-control member 8- against the thrust of the spring l0 towardthe left, thereby shifting the pump 1 into substantially neutral or nodelivery position. The outer end of the cylinder bore I1 is closed by aclosure 2| connected to the casing IS in any convenient manner, andprovided with, a bore 22 which, in

NT- optics" its turn, communicates with a conduit 23. The conduit 23leads to a conduit 24 which communicates with the pressure side of thepump 1, while allow fluid communication between the upper portionof thevalve casing 28 with the conduit 33. The valve member 29 also has alongitudinal bore 34 therethrough and is provided with an actuatingshaft or handle 35, having a transverse bore 36 therethrough.

The conduit 33 communicates with a conduit 31 leading to the upperportion of the cylinder 4 pertaining to the motor I, while the lowerportion of the cylinder 4 communicates with a conduit 38 leading to thelower portion of the fourway valve 21. The lowermost end of the fourwayvalve 21 furthermore communicates with a conduit 39 leading to theconduit 25. Communicating with the conduit 31 is a pilot line 40 whichleads to the chamber l8 of the control mechanism l5.

Communicating with the pressure line 24 is a conduit leading to aconduit 42, which communicates with the four-way valves 43 and 44. Thesevalves, in their turn, control the supply of pressure fluid to themotors 2 and 3 respectively. The valves 43 and 44 are four-way valves ofany standard design with a neutral or intermediate position, in which nofluid is admitted to nor exhausted from the motors 2 and 3. If desired,the four-way valves 43 and 44 may be of the same construction as thefour-way valve 21.

Connected to-the four-way valve 43 are two conduits 45 and 46respectively leading to the upper and lower portion of the cylinder 41pertaining to the motor 2 which, in its fundamental structure, may besimilar to the motor I. Similarly, two conduits 48 and 49 connected tothe four-way valve 44 lead to the cylinder 50 pertaining to the motor 3,which corresponds to the motor 2. A conduit interconnecting the valves43 and 44, constitutes an exhaust line and leads to the tank 26.

The various positions of the valve 21 are shown in Figures 2, 3 and 4,and will be discussed in connection with the operation of the device.

It may be assumed that it is now desired to operate the high pressuremotor I without operating the motors 2 and 3, which are cut off from theconduit 4| by placing the valves 43 and 44 in neutral position.

It may further be assumed that the pump 1 is idling. To effect operationof the motor I, the operator shifts the actuating shaft or handle 35upwardly into the position of Figure 3, thereby causing a pressure dropin the pilot line 23 so that the spring l0 moves the pump 1 on fulldelivery stroke. The fluid expelled from the upper portion of the valvecasing 28, during the upward shifting. movement of the handle 35, passesthrough bores 36 and 34 into the exhaust line 39. When the valve member29 has thus been shifted, it will be clear that pressure fluid from thepump sure prevailing in the conduit 31 is also conveyed through thepilot line 40 to the chamber ll of the control mechanism I5. The piston5 now performs its working stroke. 1

When, at the end or during any point of this workingstroke, apredetermined maximum pressure has been built up in the upper portion ofthe press cylinder 4, this pressure acts through the pilot line 49 onthe annular area 52 of the differential piston l9, while the samepressure position.

acts through pilot line 23 on the larger differential area 53 of thepiston l9. This diflerenti'al pressure then causes the piston l9 to moveinto the position shown in Figure 1, thereby shifting the pump tosubstantially neutral or no delivery In other words, the pump 1 is nowidling at the maximum pressure required in the hydraulic system.

If, at this time, it is not required'to hold the piston 5 under itsmaximum pressure, the valve member 29 may be moved into intermediate orneutral position, in which instance the chamber |8 will be connected tothe exhaust line 25 through the pilot line 40. conduit 33, slots 32,bores 36 and 34 and th conduit 39. quently, the pressure actinin thebore I1 of the control device l5 will not Lir' opposed by pressure inthe chamber l8 so that tne pump 1 will be held in its idling position ata low pressure.

If it is desired to retract the piston 5, the operator shifts the shaftor handle 35 into the position of Figure 4, thereby again creating apressure drop in the pilot line 2 so that the pump 1 is again moved intofull delivery position by the spring Hi. Pressure fluid from the pump 1then passes through the conduits 24 and 38 into the lower portion of thecylinder 4, while the upper portion of the cylinder 4 is connectedthrough the conduits 31 and 33, the bores35 and 34 and the conduit 39with the suction line 25.

1 passes through conduit 24 into the conduit 33,

and from there through conduit 31 into the upper Consequently, thepiston 5 moves upwardly.

When the piston 5 has reached the end of its retraction stroke, namely,the position shown in Figure 1, and is halted, the pressure in conduits38 and 24 acts through pilot line 23 on the differential area 53 of thepiston l9 so as to shift the pump 1 to neutral or no delivery positionagainst the thrust of the spring ID. The

operator may then shift the valve member 29 back into its neutralposition, as shown in Figure 1. The hydraulic system is then again inits initial or idling position, shown in Fgure 1. It will be noted that,in this position, pressure acts on'the larger differential area 53 onlyand not on 1 the smaller differential area 52, so that the pump 1 isheld in its idling position at the lowest pressure required in thesystem.

If it is now desired to operate the low pressure motors 2 and 3, theoperator shifts the valves 43 and 44 so as to establish fluid connectionbetween the conduits 45 and 43 with the conduit 4|, while simultaneouslyconnecting the conduits 46 and 49 with the exhaust line 5|. This causesa pressure drop in the pilot line 23 so that the spring I0 again shiftsthe pump 1 into full delivery position. Fluid pressure, therefore,passes through conduits 24 and 4| and the conduits 45 and 48 to themotors 2 and 3 respectively, while fluid expelled therefrom is exhaustedthrough conduits 46 and 49 to the tank '26.

The fluid pressure prevailing in conduit 4| is conveyed through thepilot line 23 to the larger differential area 53 of the differentialpiston l9,

Consewhile the conduit 46 communicates through the conduit 33, slots32,.bores-3'6 and 34 and conduit the conduits 45' and 48, which maximumpressure is lower than the required maximum pressure in the motor I, thepressure in conduits 45 and 48 acts through pilot line 23 upon thelarger area 53 of the difierential piston l9 so as to cause movement ofthe pump 1 into substantially neutral or no delivery position.

To return the motors 2 and 3 to their initial position, the operatorreverses the position of the valves 43 and 44, thereby again causing apressure drop in the pilot line 23 so that the spring l again moves thepump 1 intofull delivery position. Fluid pressure from the pump 1 thenpasses through conduits 4|, 46 and 49 into the lower portion of thecylinders 41 and 5!) respectively, thereby bringing about a retractionstroke of the motors 2 and 3. 7

When, at he close of this retraction stroke, a predetermined pressurehas built up in the conduit 4|, this pressure acts through the pilotline 23 on the larger difierential area 53 of the dif ferential pistonl9 again, and returns the pump 1 to its neutral or no delivery po itionin the manner previously described. The valves 43 and the motors I 2 and3 could be operated at the maximum pressure required in the system byshifting the three four-way valves 21, 43 and 44.

Referring now to the embodiment of Figure 5, the system shown therein issimilar to that shown in Figure 1, and similar parts are, therefore,designatedwith the same reference numerals as in the system of Figure 1,however, with the additional letter a. I

The system of Figure 5 differs from that of Figure 1 primarily in thatthe motors la, 2a and pressure motor, and the motor 311 is a lowpressure motor. Furthermore, the control mechanism l5 of Figure 1 isreplaced by a control mechanism 54, which comprises a casing with threechambers 56, 51 and 58. Reciprocably mounted in the chamber 56 is adifferential piston 59 having a larger differential area 60 and asmaller diii'erential area 6|. The piston 59 is furthermore connectedwith a control rod 62 for shifting the flow-control member 8a. ofthepump Ia. A sleeve-like floating plunger 63 is adapted to be actedupon by pressure fluid in the chamber 58, and to slide on the rod 62 soas to engage the piston 59.

The conduit system connecting thepump la with the high pressure motor Iaand low pressure motor 3a corresponds to that of Figure 1. The

, conduit-system pertaining to the medium pressure motor 211 comprises aconduit 64 leading from the chamber 58 in the control mechanism by abranch line 65 with-theupperportion of the cylinder 41a. The rest of theconduit system pertaining to the medium pressure motor 2a corresponds tothe low pressure motor 2 of Figure 1.

The operation of the maximum pressure motor la in Figure 5 correspondsto that of the maximum pressure motor I' of Figure 1. To ef-' feet adownward stroke of the piston 5a, the operator shifts the valve handle35a upwardly, thereby causing a pressure 'drop in the pilot line. 23a sothat the pump-1a moves on full delivery stroke and delivers pressurefluid into the upper portion of the cylinder 4a, while fluid expelledfrom the lower portion of the cylinder 4a is exhausted into the tank26a. When a predetermined maximum pressure has been established in theupper portion of the cylinder 4a, this pressure, which is conveyedthrough the pilot line 40a into the chamber 51 to act on the smallerdifierential area BI and is also conveyed through the pilot line 23a tothe chamber 56 to act on the larger differential area 60, causes thedifferential piston 59 to move the pump 1a into substantially neutralor' no delivery position, as shown in Figure 5.

To reverse the movement of the piston 5a, the operator reverses theposition of the valve handle 35a, thereby again bringing about apressure drop in the pilot line 23a and causing the pump 1a to return toits full delivery stroke position. Pressure fluid from the pump 1a isthen conveyed into the lower portion of the cylinder 4a, while fluidfrom the upper portion of the cylinder 4a is exhausted into the tank26a. When a predetermined pressure, lower than the maximum pres-; sureobtained during the downward stroke of the motor la, has beenestablished, this pressure acts through pilot line 23a on the piston 59,so as to move the pump 1a to substantially neutral or no deliveryposition. It will be noted that the pilot line 40a is now connected toan exhaust or the tank 26a. The pump 1a, therefore, now idles at thelowest pressure required in the hydraulic system. The operator may nowreturn the valve member 29a to its neutral position, as shown in Figure5.

To operate the medium pressure motor 2a, the operator shifts the valvemember pertaining to the valve 43a into its uppermost position so that apressure drop occurs in the pilot line 23a, and the spring Illa. returnsthe pump la, to full delivery position. Pressure fluid thenflows throughthe conduit 24a and the conduit 65 into the upper portion of thecylinder 41a, while fluid expelled from the lower portion of thecylinder 41a is exhausted through conduits 5la and 39a into the tank2611. It will be clear from the drawings that the pressure prevailing inthe,

conduits 24a and 65 is conveyed through the pilot line 64 into thechamber 58 .and through pilot line 230. into the chamber 56.Consequently, the

toward the left, thereby shifting the pump la into substantially neutralor no delivery position. The pump is now idling at a medium pressure. Ifthe motor 2a is not to be held under pressure,

the valve 43a may be shifted into its neutral position so that thechamber 58 will be connected through conduit 64 and the slots 32a, thebores 35a and 34a and the conduit 5la with the tank 16a so that thepressure acting in the chamber 56 is not opposed by pressure in thechamber 58, with the result that the pump la will idle at the lowestpressure required in the hydraulic system. To reverse the medium motor2a, the operator shifts the valve 43a into its lowermost position,thereby again creating a pressure drop in the pilot line 23a so that thespring I0a returns the pump Ia to full delivery position. The conduitsGI .and 65 are then connected to the tank 26a, while pressure fluidflows to the lower portion of the cylinder 41a through the conduit 46a.The motor 211 then returns to its upper position. When, at the end ofthis return stroke, a predeterminedlow pressure has been established,this pressure acts through the pilot line 23a on the piston 59 and movesthe pump To to substantially neutral or no delivery position. The pumpthen idles-at low pressure. The valve 4311 may then be returned to itsneutral position.

The operation of the motor 3a fully corresponds to the operation of themotor 3, so that no further description is required. When, thepredeterminedmaximum pressure required for the motor 3a has beenestablished therein, which maximum pressure is lower than the requiredmaximum pressure of the motor Ia and the motor 2a, the pump la is'shifted to substantially neutral or no delivery position and then idlesat low pressure.

From the above, it will be clear that the hydraulic system according tothe present invention enables the operation of a plurality of motors atdifierent maximum pressures respectively required for these motorswithout having to idle the pump at the highest required maximumpressure. On the contrary, the pump may idle at the lowest maximumpressure required, thereby saving considerably in power and materiallyincreasing the life of the pump.

' It will be understood that I desire to comprehend within my inventionsuch modifications as come within the scope .of the claims.

Having thus fully described my invention, what I claim as new and desireto secure by Letters Patent, is:-

1. In a hydraulic system, a high pressure motor, a low pressure motor,each of said motors including a reciprocable plunger and fluid operableadvancing and; retracting means for actuating .s aid'plungena variabledelivery pump for supplying pressure fluid selectively to said advancing or retracting means, means for continuously urging said pumpinto fulldelivery stroke position, pump control means for opposing theaction of said urging means and including a difierential piston with alarger area and a smaller 'opposed area, first conduit meanscontinuously establishing fluid connection between the pressure side ofsaid pump andsaid larger area, seco'nd conduit means continuouslyestablishing fluid connection between said smaller diiferential area andthe advancing means pertaining to said high -pressure"motor, andseparate valve means for controlling the supply or fluid from said pumpto each of said motors. i

- 2. In a hydraulic system; a high pressure motor, a-lowpressure motor,each of said motors having associated therewith fluid operable advancingand retracting means for causing said. motor to eflect an advancing anda retracting advancing means of said high pressure motor,

and separate valve means respectively associated with said high pressureand said low pressure motors for controlling the supply of fluid betweensaid source and each of said motors.

3. In a. hydraulic system, a high pressure motor, a low pressure motor,each of said motors hav n associated therewith fluid operable advancingand retracting means for actuating said motors, a pressure fluid sourcefor selectively supplying pressure fluid .to said advancing orretracting means of either of said motors, control means associated withsaid fluid source for varying the delivery thereof, means forcontinuously urging said control means into position to bring aboutmaximum delivery of said fluid source, fluid pressure responsivemechanism operable to'counteract said control means for reducing thedelivery of said fluid source, said mechanism comprising a difierentialplunger with a larger area continuously connected to said fluid pressuresource, and also comprising a smaller area opposed to the larger areaand continuously connected with the advancing means pertaining to saidhigh pressure motor, and separate valve means respectively lic motors,each requiring a difierent maximum operating pressure, each of saidmotors having associated therewith fluid operable advancing andretracting means for actuating the respective motor, a fluid sourcecommon to said motors for supplying pressure fluid thereto, controlmeans associated with said fluid source for varying the deliverythereof, means for continuously urging said control means to bring aboutmaximum delivery of said 'fluid source, pressure responsive mechanismfor actuating said control means to reduce the delivery of said fluidsource, said mechanism including a differential plunger having itslargest effective area continuously connected to saidpressure'fluidsource, and having a smaller efiective area opposed to the largest areaand communicating with the advancing means of one of said motors, andseparate valve means for each mot controlling the flow of fluid betweensaid source ..nd each of LJ-id motors.

5. In a hydraulic system, a plurality of hydraulic motors, eachrequiring a difierent maximum operating pressure, each of said motorshaving associated therewith fluid operable advancing fluid source, andhaving a smaller efiective area opposed to-the larger area communicatingwith the advancing means of one of said motors, means for continuouslyurging said control means to bring about maximum delivery of said fluidsource, and a plurality of control valves respectively associated withsaid motors for controlling the flow of fluid to and from said motors,each of said control valves comprising a balanced valve member with alongitudinal bore therethrough hydraulically connected at one end withpassageways on said valve member and connected at the other end with anexhaust.

6. In a hydraulic system, three motors respectively requiring threedifierent maximum operating pressures, each of said motors includingfluid operable advancing and retracting means for actuating said motors,a variable delivery pump common to said motors for selectively supplyingpressure fluid to said advancing or retracting means,

means for continuously urging said pump into full delivery position,pressure-responsive means associated with said pump andincludingdifierential plunger means with three difierent effective areas, firstconduit means continuously connecting the largest of said areas with thepressure side of said pump, second conduit means continuously connectingthe second largest of said areas with the advancing means pertaining tothe motor requiring the highest operating pressure, third conduit meanscontinuously connecting the smallest of said efr'ectiveareas with theadvancing means pertaining to the motor requiring the second highestmaximum pressure, said second and third areas being opposed'to saidfirst area and separate valve means for controlling the supply of

